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#1240 by meberbs on 05 Sep, 2017 22:25
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Meberbs, I think you are coming close to stretching your interpretation of the Navy's own words . . .
Did you not read the rest of the discussion before posting? I already said I misinterpreted part of that sentence, but they clearly aren't focused on that second design. -
#1241 by graybeardsyseng on 05 Sep, 2017 23:07
-
A bit about the US Navy EmDrive work has surfaced:
https://info.aiaa.org/tac/PEG/NFPTC/Shared%20Documents/abstract_Mcdonald.pdf
Seems the project lead, Mike McDonald, is credible:
https://www.linkedin.com/in/mike-mcdonald-36447050/
Roger's interesting comment on the attached was:
"It is good to see that the US Naval Research Lab has broken cover.
As always, leading the way. Go Navy!
Some history.
https://www.nrl.navy.mil/ssdd/ncst/
Bravo Zulu - GO NAVY Indeed. I am VERY excited to hear they are involved and waiting with worm on tongue for their results. Sierra Hotel.
In my experience NRL has some of the best most capable and critical minds today. Yes - I am a bit biased towards Navy (see my sig line or my linkedin profile) BUT I also worked with them as a SE or PE for various civilian contractors on several projects over maybe 30 years and without exception found them absolutely committed to obtaining results which are solid (whether positive, negative or whatever). I am really looking forward to their design and their results. One advantage of being an old f**t is worked with a lot of folks and developing a strong feeling for whom you can depend of for solid data. In my experience NRL is one of those groups.
Just one other suggestion - those members who approach the EMDrive critically and who try to find the problems and difficulties, who force us to examine flaws etc with new theories and experimental approaches are one of our most valuable resources here. Each time they point out a problem and a theory or experiment is improved to address that problem we are closer to a BELIVABLE answer to "does it work". So perhaps we should not question the motives of someone questioning the EMDrive - they are doing some heavy lifting whether or not it works.
Personally - I HOPE it works, I THINK or perhaps FEEL based on decades of RF experimentation, that it might - and neither of those is worth a bucket of warm spittle. I want to KNOW, we NEED to know, and that takes carefully critically obtained DATA. DATA which are challenged, questioned; with strong robust attempts to refute them. As someone said some pages back - no a flying car WON'T be sufficient. But 1 micro-newton of excess thrust critically and objectively PROVEN will be earth shaking.
And the provable, internally and externally consistent theory as to how that micro-newton of force got there is going to put someone's name on a new chair(s) in some very prestigious physics department(s). And probably a trip to Sweden. Likewise data and theory which PROVE this a long stern chase of non-domestic geese will allow some great minds to move on and work on the next step on getting humankind off this mudball.
Herman
graybeardsyseng
-
#1242 by birchoff on 06 Sep, 2017 00:19
-
A bit about the US Navy EmDrive work has surfaced:
https://info.aiaa.org/tac/PEG/NFPTC/Shared%20Documents/abstract_Mcdonald.pdf
Seems the project lead, Mike McDonald, is credible:
https://www.linkedin.com/in/mike-mcdonald-36447050/
Roger's interesting comment on the attached was:
"It is good to see that the US Naval Research Lab has broken cover.
As always, leading the way. Go Navy!
Some history.
https://www.nrl.navy.mil/ssdd/ncst/
Bravo Zulu - GO NAVY Indeed. I am VERY excited to hear they are involved and waiting with worm on tongue for their results. Sierra Hotel.
In my experience NRL has some of the best most capable and critical minds today. Yes - I am a bit biased towards Navy (see my sig line or my linkedin profile) BUT I also worked with them as a SE or PE for various civilian contractors on several projects over maybe 30 years and without exception found them absolutely committed to obtaining results which are solid (whether positive, negative or whatever). I am really looking forward to their design and their results. One advantage of being an old f**t is worked with a lot of folks and developing a strong feeling for whom you can depend of for solid data. In my experience NRL is one of those groups.
Just one other suggestion - those members who approach the EMDrive critically and who try to find the problems and difficulties, who force us to examine flaws etc with new theories and experimental approaches are one of our most valuable resources here. Each time they point out a problem and a theory or experiment is improved to address that problem we are closer to a BELIVABLE answer to "does it work". So perhaps we should not question the motives of someone questioning the EMDrive - they are doing some heavy lifting whether or not it works.
Personally - I HOPE it works, I THINK or perhaps FEEL based on decades of RF experimentation, that it might - and neither of those is worth a bucket of warm spittle. I want to KNOW, we NEED to know, and that takes carefully critically obtained DATA. DATA which are challenged, questioned; with strong robust attempts to refute them. As someone said some pages back - no a flying car WON'T be sufficient. But 1 micro-newton of excess thrust critically and objectively PROVEN will be earth shaking.
And the provable, internally and externally consistent theory as to how that micro-newton of force got there is going to put someone's name on a new chair(s) in some very prestigious physics department(s). And probably a trip to Sweden. Likewise data and theory which PROVE this a long stern chase of non-domestic geese will allow some great minds to move on and work on the next step on getting humankind off this mudball.
Herman
graybeardsyseng
While they will not be evaluating theory in their work. I wonder why they even bothered including talk about Mach Effect thruster. The devices that have been shown to work under that particular theory are configured in a completely different manner. To date unless I missed something, linking Resonant cavity force measurements to ME theory is mostly theoretical conjecture at this point. -
#1243 by Monomorphic on 06 Sep, 2017 01:02
-
I don't know how hard it would be to shift the vertical LDS to a horizontal LDS at the other end. If it were easy enough, you could try it on a test and estimate the non-torsional movement as above. If it turns out to be small enough to ignore, you could move it back. If not, you'd have to decide what to do next....
Not very hard at all. The cables are long enough to reach if I move the electronics up to the height of the pendulum. This was planned for other reasons, so I went ahead and included the ability for dual optical sensors, that are mirrored as exactly as possible on opposite sides. Just two nuts to remove and one can be moved back into the vertical detection orientation.
With any luck the 30W amplifier will be operational in the next few days. Then a great deal of calibrating.
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#1244 by Mulletron on 06 Sep, 2017 02:17
-
A bit about the US Navy EmDrive work has surfaced:
https://info.aiaa.org/tac/PEG/NFPTC/Shared%20Documents/abstract_Mcdonald.pdf
Seems the project lead, Mike McDonald, is credible:
https://www.linkedin.com/in/mike-mcdonald-36447050/
Roger's interesting comment on the attached was:
"It is good to see that the US Naval Research Lab has broken cover.
As always, leading the way. Go Navy!
Some history.
https://www.nrl.navy.mil/ssdd/ncst/
Bravo Zulu - GO NAVY Indeed. I am VERY excited to hear they are involved and waiting with worm on tongue for their results. Sierra Hotel.
In my experience NRL has some of the best most capable and critical minds today. Yes - I am a bit biased towards Navy (see my sig line or my linkedin profile) BUT I also worked with them as a SE or PE for various civilian contractors on several projects over maybe 30 years and without exception found them absolutely committed to obtaining results which are solid (whether positive, negative or whatever). I am really looking forward to their design and their results. One advantage of being an old f**t is worked with a lot of folks and developing a strong feeling for whom you can depend of for solid data. In my experience NRL is one of those groups.
Just one other suggestion - those members who approach the EMDrive critically and who try to find the problems and difficulties, who force us to examine flaws etc with new theories and experimental approaches are one of our most valuable resources here. Each time they point out a problem and a theory or experiment is improved to address that problem we are closer to a BELIVABLE answer to "does it work". So perhaps we should not question the motives of someone questioning the EMDrive - they are doing some heavy lifting whether or not it works.
Personally - I HOPE it works, I THINK or perhaps FEEL based on decades of RF experimentation, that it might - and neither of those is worth a bucket of warm spittle. I want to KNOW, we NEED to know, and that takes carefully critically obtained DATA. DATA which are challenged, questioned; with strong robust attempts to refute them. As someone said some pages back - no a flying car WON'T be sufficient. But 1 micro-newton of excess thrust critically and objectively PROVEN will be earth shaking.
And the provable, internally and externally consistent theory as to how that micro-newton of force got there is going to put someone's name on a new chair(s) in some very prestigious physics department(s). And probably a trip to Sweden. Likewise data and theory which PROVE this a long stern chase of non-domestic geese will allow some great minds to move on and work on the next step on getting humankind off this mudball.
Herman
graybeardsyseng
While they will not be evaluating theory in their work. I wonder why they even bothered including talk about Mach Effect thruster. The devices that have been shown to work under that particular theory are configured in a completely different manner. To date unless I missed something, linking Resonant cavity force measurements to ME theory is mostly theoretical conjecture at this point.
Maybe it's better to separate ME theory from the Woodward devices and then look at the commonalities of those devices to that of EMdrive. -
#1245 by dustinthewind on 06 Sep, 2017 04:17
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Belief is irrelevant, and the math says he is very wrong. Clearly he just calculated the kinetic energy of the device and did not account for any of the energy in the fields.You say I don't understand them and am going off half (maybe all) cocked. Do you really think they would write all those papers if all they were saying is "Hey, here's an interesting way to make a propellent-less propulsion device that works far far less efficiently than a simple photon rocket and is entirely useless!!!!!"? Or maybe, "Hey, this would work but you need gigawatts of power!!!! Maybe that's the academic world but somehow, I doubt that. So, what do you think they are really trying to say with these papers?
I have no idea why they haven't calculated the power requirements, especially since there is an easy way to do so since the energy flux is equal to c times the momentum flux. Them not calculating it in no way changes the fact that this is a ton of power, and yes it probably would melt something if you tried to build such a device.
Can you realistically imagine proposing gigawatt levels of power in meter sized coils carrying 100 amps of current? Wouldn't they just melt?
It does not matter why they aren't discussing the power numbers, because the power numbers are what they are. Do you have anything to add that is actually based on math or physics?
I emailed one of the authors, professor Yahalom, about the power levels for that 2.74N force and I'll let you know if he answers.
I got an answer. He said using his concept a 100 kg device should get to a speed of 1m/s with 50 Joules where a photon rocket requires 3E10 Joules to do the same. So he thinks it's not just in effect a photon rocket. But I did ask for further clarification that he specifically state the fields carry away more momentum than a simple photon rocket if that's what he believes.
I think it's clear I wasn't suggesting he simply believes this or that as an article if faith and not by a scientific argument. And he does calculate the energy of the fields here;
https://arxiv.org/abs/1302.2537v2
Updated with a new title here;
https://arxiv.org/pdf/1302.2537v3.pdf
I suggested to him by email that he explicitly compare his device to a photon rocket and he said that was a good idea and might be a future paper.
Hi Bob, this paper looks very similar to the one you pulled up. Linked here: DEF: The Physical Basis of Electromagnetic Propulsion by Mario J. Pinheiro He references White's quantum vacuum propulsion I think. Seems to emphasize time delayed near field interaction. It strikes me he mentions using the Barium Titanate at low frequency. -
#1246 by Chrochne on 06 Sep, 2017 06:25
-
A bit about the US Navy EmDrive work has surfaced:
https://info.aiaa.org/tac/PEG/NFPTC/Shared%20Documents/abstract_Mcdonald.pdf
Seems the project lead, Mike McDonald, is credible:
https://www.linkedin.com/in/mike-mcdonald-36447050/
Roger's interesting comment on the attached was:
"It is good to see that the US Naval Research Lab has broken cover.
As always, leading the way. Go Navy!
Some history.
https://www.nrl.navy.mil/ssdd/ncst/
Good read thank you.
It looks like Mr. McDonald and his team will be attending The 35th International Electric Propulsion Conference (IEPC) is scheduled for October 8 – 12, 2017 on the Georgia Institute of Technology campus in Atlanta.
He is mentioned in here - https://iepc2017.org/preliminary-technical-program
First page 10:00, Track 8
Thrust Measurement and Error Analysis of the IMPULSE Resonant Microwave Cavity Drive
Michael S. McDonald,
Michael W. Nurnberger,
Logan T. Williams
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#1247 by ThatOtherGuy on 06 Sep, 2017 08:34
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@monomorphic (and possibly others)
I just stumbled upon this piece of software which allows to write code to easily interface to various instruments, while it may be somewhat OT, I decided to post it here since it may be useful to EMdrive builders and experimenters
https://www.codeproject.com/Articles/11033/FreeCal-GPIB-Instrument-Automation-for-Metrology-T
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#1248 by TheTraveller on 06 Sep, 2017 11:18
-
Just received from Roger:
Hi Phil,
As there seem to be a significant number of experiments in the public domain that are not achieving anywhere near viable thrust values, I have put together the attached short note on general principles of EmDrive design and manufacture.
Hopefully this will illustrate that although the theory is relatively straightforward, the engineering of a successful EmDrive is difficult. It requires the knowledge, patience and tenacity exhibited by all successful microwave engineers. I am sure you are well aware of this.
Feel free to share.
Best regards
Roger
General Principles for the successful design and manufacture of an EmDrive Thruster
1. Design the cavity for the required operating frequency and mode, at a specified temperature. Do not just make a cavity and then find out what the resonant frequency is. This has been the case for a number of experimenters who have either obtained no thrust or have achieved only a very low level of thrust.
2. The design should aim for a clear separation of operating frequency and mode from the various possible modes. A series of designs should be undertaken as part of a full model analysis. The operating mode must remain above cut-off at the small end of the cavity.
3. For a narrow band microwave source, the cavity geometry should include shaped end plates to ensure that wave-front phase distortion, which results in a bandwidth spread, does not limit the Q of the cavity. Clearly correct geometric alignment is impossible with flat end plates. Spherical end plates with correct radii are the simplest option.
4. The cavity design should be initially tested with a swept frequency to identify the resonant frequencies of the required mode and adjacent modes. A successful design and build will give an initial resonant frequency within a maximum of 0.5% of design value, at the specified temperature.
5. Cavity manufacture to high tolerance is essential to obtain high Q at the specified resonant frequency. Manufacturing tolerance should be around ±0.01mm.
6. Assembly of the cavity must include an end plate alignment process to obtain a Q of at least 50,000. Low Q values are unlikely to give predicted thrust values, as they are a sign of poor design or manufacture.
7. Whatever input circuit is used, loop, slot, dipole etc., it must be designed and tested to deliver a good match between the wave impedance of the cavity at the input position, and the microwave source impedance. Input tuning is inevitably a sensitive and lengthy adjustment process.
8. A correctly matched input circuit will give a loaded Q value of half that of the natural unloaded Q. Optimum match can be checked by measuring internal cavity power using a small detector probe positioned at E field maximum. The probe should be designed to give an output at least 20dB down on input power to avoid loading the cavity.
9. Thrust measurement requires a clear understanding of Newtonian principles, as applied to a propellantless thruster. Expecting to measure thrust as if EmDrive is a conventional propulsion system will lead to ambiguous results. Ideally, thrust should be calculated by measuring the acceleration of a freely suspended thruster, and then applying Newton’s laws.
-
#1249 by TheTraveller on 06 Sep, 2017 11:55
-
6. Assembly of the cavity must include an end plate alignment process to obtain a Q of at least 50,000. Low Q values are unlikely to give predicted thrust values, as they are a sign of poor design or manufacture.
Number 6 is critical to achieving good thrust.
I have mentioned this before.
Any EmDrive builder that does not design in the ability to adjust end plate parallelism may be disappointed with achieved thrust, even when the thruster is built to +-10um dimensional tolerance and all interior surfaces are polished to astronomical quality.
I use dual O rings and 8 equally spaced bolts to adjust end plate flange to side wall flange O ring compression to obtain max Q and optimal end plate parallelism. -
#1250 by Monomorphic on 06 Sep, 2017 13:01
-
More from Michael McDonald regarding Roger Shawyer and their second frustum:
"I have neither a working EMDrive nor have I ever interacted with Roger Shawyer. If the abstract mentioned our own design it’s due to poor editing. I wrote an earlier version I wrote when I thought we’d be making one of our own. I thought I had updated it to present correctness, but I guess not. " -
#1251 by PotomacNeuron on 06 Sep, 2017 14:02
-
Just received from Roger:
Hi Phil,
As there seem to be a significant number of experiments in the public domain that are not achieving anywhere near viable thrust values, I have put together the attached short note on general principles of EmDrive design and manufacture.
Hopefully this will illustrate that although the theory is relatively straightforward, the engineering of a successful EmDrive is difficult. It requires the knowledge, patience and tenacity exhibited by all successful microwave engineers. I am sure you are well aware of this.
Feel free to share.
Best regards
Roger
General Principles for the successful design and manufacture of an EmDrive Thruster
1. Design the cavity for the required operating frequency and mode, at a specified temperature. Do not just make a cavity and then find out what the resonant frequency is. This has been the case for a number of experimenters who have either obtained no thrust or have achieved only a very low level of thrust.
2. The design should aim for a clear separation of operating frequency and mode from the various possible modes. A series of designs should be undertaken as part of a full model analysis. The operating mode must remain above cut-off at the small end of the cavity.
3. For a narrow band microwave source, the cavity geometry should include shaped end plates to ensure that wave-front phase distortion, which results in a bandwidth spread, does not limit the Q of the cavity. Clearly correct geometric alignment is impossible with flat end plates. Spherical end plates with correct radii are the simplest option.
4. The cavity design should be initially tested with a swept frequency to identify the resonant frequencies of the required mode and adjacent modes. A successful design and build will give an initial resonant frequency within a maximum of 0.5% of design value, at the specified temperature.
5. Cavity manufacture to high tolerance is essential to obtain high Q at the specified resonant frequency. Manufacturing tolerance should be around ±0.01mm.
6. Assembly of the cavity must include an end plate alignment process to obtain a Q of at least 50,000. Low Q values are unlikely to give predicted thrust values, as they are a sign of poor design or manufacture.
7. Whatever input circuit is used, loop, slot, dipole etc., it must be designed and tested to deliver a good match between the wave impedance of the cavity at the input position, and the microwave source impedance. Input tuning is inevitably a sensitive and lengthy adjustment process.
8. A correctly matched input circuit will give a loaded Q value of half that of the natural unloaded Q. Optimum match can be checked by measuring internal cavity power using a small detector probe positioned at E field maximum. The probe should be designed to give an output at least 20dB down on input power to avoid loading the cavity.
9. Thrust measurement requires a clear understanding of Newtonian principles, as applied to a propellantless thruster. Expecting to measure thrust as if EmDrive is a conventional propulsion system will lead to ambiguous results. Ideally, thrust should be calculated by measuring the acceleration of a freely suspended thruster, and then applying Newton’s laws.
I think those principles make it very difficult to carry out an EmDrive experiment. I think the EW's, Tajmar's, and himself's experiments are all invalidated by this or that point. Even monomorphic's is invalidated---- no way the inner finish is to 0.01mm tolerance with the foils glued on. The Navy's new experiment is invalidated because of its flat ends, either.
Some are not logical either. I do not see the difference of making a frustum within 0.5% to targeted frequency, and making a similarly shaped one then choosing frequency to match the frustum.
-
#1252 by flux_capacitor on 06 Sep, 2017 14:26
-
More from Michael McDonald regarding Roger Shawyer and their second frustum:
"I have neither a working EMDrive nor have I ever interacted with Roger Shawyer. If the abstract mentioned our own design it’s due to poor editing. I wrote an earlier version I wrote when I thought we’d be making one of our own. I thought I had updated it to present correctness, but I guess not. "
Can you ask Mike McDonald why he hasn't yet/doesn't want to "interact" with Roger Shawyer? This seems weird to me, as Eagleworks achieved very little thrust (if not at all, since the measured forces have perhaps been masqueraded with potential systematic experimental errors) whereas Shawyer claims much better experimental achievements for many years, using tighter geometries wrt "cuttoff conditions", Df and pulsed operation. Plus he often answers messages and provides assistance, as you experienced yourself. -
#1253 by OnlyMe on 06 Sep, 2017 14:34
-
A bit about the US Navy EmDrive work has surfaced:
https://info.aiaa.org/tac/PEG/NFPTC/Shared%20Documents/abstract_Mcdonald.pdf
Seems the project lead, Mike McDonald, is credible:
https://www.linkedin.com/in/mike-mcdonald-36447050/
Roger's interesting comment on the attached was:
"It is good to see that the US Naval Research Lab has broken cover.
Take the following with a grain or two of salt since I am not a builder or even a contributor to any of the design models.., and have no fundamental background in microwave technology. That said...
While it is encouraging that a lab at least associated with, if not directly supported by the US Navy, it concerns me that the limited information from the above link, suggests that they will be just replicating the Eagle Works build with relatively minor improvements.., "This experimental effort focuses on the cavity point design of White et. al from NASA JSC in Ref. [1] as both the best-described and only peer-reviewed result currently available, and reproduces their cavity geometry while re-engineering the fabrication technique and microwave (RF) power feed system into the cavity.". The issue to me here being that if I remember correctly the Eagle Works build wound up resonating at a TM mode while it seems most modeling, anecdotal information and DIY designs suggest better results from builds designed around TE resonant modes.
While it is true that the Eagle Works effort has been the best documented and peer reviewed experimental test of the involved design concepts, their specific design and resulting resonant mode may not represent the best case basic design. -
#1254 by TheTraveller on 06 Sep, 2017 14:40
-
Just received from Roger:
Hi Phil,
As there seem to be a significant number of experiments in the public domain that are not achieving anywhere near viable thrust values, I have put together the attached short note on general principles of EmDrive design and manufacture.
Hopefully this will illustrate that although the theory is relatively straightforward, the engineering of a successful EmDrive is difficult. It requires the knowledge, patience and tenacity exhibited by all successful microwave engineers. I am sure you are well aware of this.
Feel free to share.
Best regards
Roger
General Principles for the successful design and manufacture of an EmDrive Thruster
1. Design the cavity for the required operating frequency and mode, at a specified temperature. Do not just make a cavity and then find out what the resonant frequency is. This has been the case for a number of experimenters who have either obtained no thrust or have achieved only a very low level of thrust.
2. The design should aim for a clear separation of operating frequency and mode from the various possible modes. A series of designs should be undertaken as part of a full model analysis. The operating mode must remain above cut-off at the small end of the cavity.
3. For a narrow band microwave source, the cavity geometry should include shaped end plates to ensure that wave-front phase distortion, which results in a bandwidth spread, does not limit the Q of the cavity. Clearly correct geometric alignment is impossible with flat end plates. Spherical end plates with correct radii are the simplest option.
4. The cavity design should be initially tested with a swept frequency to identify the resonant frequencies of the required mode and adjacent modes. A successful design and build will give an initial resonant frequency within a maximum of 0.5% of design value, at the specified temperature.
5. Cavity manufacture to high tolerance is essential to obtain high Q at the specified resonant frequency. Manufacturing tolerance should be around ±0.01mm.
6. Assembly of the cavity must include an end plate alignment process to obtain a Q of at least 50,000. Low Q values are unlikely to give predicted thrust values, as they are a sign of poor design or manufacture.
7. Whatever input circuit is used, loop, slot, dipole etc., it must be designed and tested to deliver a good match between the wave impedance of the cavity at the input position, and the microwave source impedance. Input tuning is inevitably a sensitive and lengthy adjustment process.
8. A correctly matched input circuit will give a loaded Q value of half that of the natural unloaded Q. Optimum match can be checked by measuring internal cavity power using a small detector probe positioned at E field maximum. The probe should be designed to give an output at least 20dB down on input power to avoid loading the cavity.
9. Thrust measurement requires a clear understanding of Newtonian principles, as applied to a propellantless thruster. Expecting to measure thrust as if EmDrive is a conventional propulsion system will lead to ambiguous results. Ideally, thrust should be calculated by measuring the acceleration of a freely suspended thruster, and then applying Newton’s laws.
I think those principles make it very difficult to carry out an EmDrive experiment. I think the EW's, Tajmar's, and himself's experiments are all invalidated by this or that point. Even monomorphic's is invalidated---- no way the inner finish is to 0.01mm tolerance with the foils glued on. The Navy's new experiment is invalidated because of its flat ends, either.
Some are not logical either. I do not see the difference of making a frustum within 0.5% to targeted frequency, and making a similarly shaped one then choosing frequency to match the frustum.
Engineering is engineering.
NONE of Roger's cavities used flat end plates set at the ends of the tapered side walls. While the EW and other cavities did use this, it is not what Roger recommends nor ever used. A tapered cavity needs spherical end plates to obtain high Q. Fact. End of discussion.
EW did not build a SPR compliant thruster as the small end diameter is too small and results in operation below practical cut-off and included a lossy dielectric. They built a thruster based on QV theory and ignored Roger's advise.
Tajmar's cavity was about as bad as it gets with a Q of around 50.
Both had force generation at the level of a few snowflakes.
Wavefront phase distortion can destroy high Q.
Maybe tell the builders of high Q accelerator cavities to use flat sides, ignore tight build tolerance, forget about optical quality polishing, no need to physically tune their cavities, and don't bother to tune their couplers to get optimal Ql?
If you want good specific force, for a Cu spherical S band TE013 thruster specific force should be around 0.3 to 0.4N / kWrf, then follow Roger's guidelines.
For sure those guidelines are not simple, easy, low cost nor quick to follow.
Bottom line is ignore the design rules, build a non compliant cavity and forget about any significant thrust.
Should add that when EW removed the dielectric, specific force increased over 3x. I have no doubt that had their cavity had a 0.82 design rule compliant small end, the specific force would have been mant times again higher.
What amazes me is why when EW knew a non dielectric TE012 cavity could produce 3.85mN/kW, they continued to use the dielectric TM212 cavity at 1.2mN/kW?
-
#1255 by PotomacNeuron on 06 Sep, 2017 14:59
-
Just received from Roger:
Hi Phil,
As there seem to be a significant number of experiments in the public domain that are not achieving anywhere near viable thrust values, I have put together the attached short note on general principles of EmDrive design and manufacture.
Hopefully this will illustrate that although the theory is relatively straightforward, the engineering of a successful EmDrive is difficult. It requires the knowledge, patience and tenacity exhibited by all successful microwave engineers. I am sure you are well aware of this.
Feel free to share.
Best regards
Roger
General Principles for the successful design and manufacture of an EmDrive Thruster
1. Design the cavity for the required operating frequency and mode, at a specified temperature. Do not just make a cavity and then find out what the resonant frequency is. This has been the case for a number of experimenters who have either obtained no thrust or have achieved only a very low level of thrust.
2. The design should aim for a clear separation of operating frequency and mode from the various possible modes. A series of designs should be undertaken as part of a full model analysis. The operating mode must remain above cut-off at the small end of the cavity.
3. For a narrow band microwave source, the cavity geometry should include shaped end plates to ensure that wave-front phase distortion, which results in a bandwidth spread, does not limit the Q of the cavity. Clearly correct geometric alignment is impossible with flat end plates. Spherical end plates with correct radii are the simplest option.
4. The cavity design should be initially tested with a swept frequency to identify the resonant frequencies of the required mode and adjacent modes. A successful design and build will give an initial resonant frequency within a maximum of 0.5% of design value, at the specified temperature.
5. Cavity manufacture to high tolerance is essential to obtain high Q at the specified resonant frequency. Manufacturing tolerance should be around ±0.01mm.
6. Assembly of the cavity must include an end plate alignment process to obtain a Q of at least 50,000. Low Q values are unlikely to give predicted thrust values, as they are a sign of poor design or manufacture.
7. Whatever input circuit is used, loop, slot, dipole etc., it must be designed and tested to deliver a good match between the wave impedance of the cavity at the input position, and the microwave source impedance. Input tuning is inevitably a sensitive and lengthy adjustment process.
8. A correctly matched input circuit will give a loaded Q value of half that of the natural unloaded Q. Optimum match can be checked by measuring internal cavity power using a small detector probe positioned at E field maximum. The probe should be designed to give an output at least 20dB down on input power to avoid loading the cavity.
9. Thrust measurement requires a clear understanding of Newtonian principles, as applied to a propellantless thruster. Expecting to measure thrust as if EmDrive is a conventional propulsion system will lead to ambiguous results. Ideally, thrust should be calculated by measuring the acceleration of a freely suspended thruster, and then applying Newton’s laws.
I think those principles make it very difficult to carry out an EmDrive experiment. I think the EW's, Tajmar's, and himself's experiments are all invalidated by this or that point. Even monomorphic's is invalidated---- no way the inner finish is to 0.01mm tolerance with the foils glued on. The Navy's new experiment is invalidated because of its flat ends, either.
Some are not logical either. I do not see the difference of making a frustum within 0.5% to targeted frequency, and making a similarly shaped one then choosing frequency to match the frustum.
Engineering is engineering.
NONE of Roger's cavities used flat end plates set at the ends of the tapered side walls. While the EW and other cavities did use this, it is not what Roger recommends nor ever used. A tapered cavity needs spherical end plates to obtain high Q. Fact. End of discussion.
EW did not build a SPR compliant thruster as the small end diameter is too small and results in operation below practical cut-off and included a lossy dielectric. They built a thruster based on QV theory and ignored Roger's advise.
Tajmar's cavity was about as bad as it gets with a Q of around 50.
Both had force generation at the level of a few snowflakes.
Wavefront phase distortion can destroy high Q.
Maybe tell the builders of high Q accelerator cavities to use flat sides, ignore tight build tolerance, forget about optical quality polishing, no need to physically tune their cavities, and don't bother to tune their couplers to get optimal Ql?
If you want good specific force, for a Cu spherical S band TE013 thruster specific force should be around 0.3 to 0.4N / kWrf, then follow Roger's guidelines.
For sure those guidelines are not simple, easy, low cost nor quick to follow.
Bottom line is ignore the design rules, build a non compliant cavity and forget about any significant thrust.
Should add that when EW removed the dielectric, specific force increased over 3x. I have no doubt that had their cavity had a 0.82 design rule compliant small end, the specific force would have been mant times again higher.
What amazes me is why when EW knew a non dielectric cavity could produce 3.8mN/kW, they continued to use the dielectric at 1.2mN/kW?
The problem is we have never seen Shawyer showing a frustum with spherical ends. We only see drawings on his patent/patents. Has he carried out experiment with spherical ends? Those experiments he claimed to achieve hundreds of mN do not have spherical ends. -
#1256 by TheTraveller on 06 Sep, 2017 15:11
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The problem is we have never seen Shawyer showing a frustum with spherical ends. We only see drawings on his patent/patents. Has he carried out experiment with spherical ends? Those experiments he claimed to achieve hundreds of mN do not have spherical ends.
PN,
Roger has stated all thruster after the 1st Experimental EmDrive used shaped end plates. So both the Demonstrator and Flight Thruster had shaped end plates.
The Flight Thruster achieved the highest measured specific force of 0.326mN/kW. While Roger has never released full dimensions for the Flight Thruster, I did confirm that it needed to use spherical end plates to resonant at 3.85GHz in TE013.
The 1st Experimental EmDrive used a tunable 1/2 wave stepped back big end plate, which is like a spherical end plate, and a tunable high Q ceramic 2.45GHz Siemens resonator at the small end, which ensured the small end did not operate below cutoff.
I'm not sure who 1st built EmDrive cavities with non stepped back flat end plates but it was not Roger.
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#1257 by OnlyMe on 06 Sep, 2017 15:40
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More from Michael McDonald regarding Roger Shawyer and their second frustum:
"I have neither a working EMDrive nor have I ever interacted with Roger Shawyer. If the abstract mentioned our own design it’s due to poor editing. I wrote an earlier version I wrote when I thought we’d be making one of our own. I thought I had updated it to present correctness, but I guess not. "
Can you ask Mike McDonald why he hasn't yet/doesn't want to "interact" with Roger Shawyer? This seems weird to me, as Eagleworks achieved very little thrust (if not at all, since the measured forces have perhaps been masqueraded with potential systematic experimental errors) whereas Shawyer claims much better experimental achievements for many years, using tighter geometries wrt "cuttoff conditions", Df and pulsed operation. Plus he often answers messages and provides assistance, as you experienced yourself.
Pay special attention to,"...whereas Shawyer claims.... Shawyer hasn't published any thing other than claims. Some of which seem they could be nothing but artifacts of his imagination, without a functioning flying car as proof. Claims are not the same as experimentally demonstrated data and/or proof.
It maybe that some of the information Shawyer provides is an interpretation of experimental observation, but he has not provided any real detail supporting the experiment(s) and much of what has been suggested can only at this point be attributed to theoretical projections based on what still seems to be faulty theory. What scales up, even based on solid theory, is not a reflection of what might be proven through engineering and manufacture.
P.S. Even patents that do not include sufficient detail to accurately reproduce any underlying claim, do not rise to the level of anything more than a "claim". -
#1258 by meberbs on 06 Sep, 2017 15:54
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9. Thrust measurement requires a clear understanding of Newtonian principles, as applied to a propellantless thruster. Expecting to measure thrust as if EmDrive is a conventional propulsion system will lead to ambiguous results. Ideally, thrust should be calculated by measuring the acceleration of a freely suspended thruster, and then applying Newton’s laws.
This in itself is enough reason to ignore everything Shawyer says. Shawyer has demonstrated that he can't even do the most basic of force balances, and simply makes logically contradictory claims. Shawyer fails his own criteria so hard here, it can't even be used as a joke.
This list seems intended to do a run around to make sure that no one can ever do a competent experiment that demonstrates once and for all that the emDrive does not work. You can bet that if someone ever met all of those criteria, Shawyer would change the statement "thrust is proportional to Q, but Q < 50000 is a cutoff below which it doesn't work" to raise this cutoff to something physically impossible to build.
I am disappointed to see that Monomorphic "liked" this post, since it means we will never see his results. He already was on the verge of getting some good data with good calibration runs that brought the noise very low, before he stopped for months to completely change his setup. -
#1259 by PotomacNeuron on 06 Sep, 2017 16:45
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9. Thrust measurement requires a clear understanding of Newtonian principles, as applied to a propellantless thruster. Expecting to measure thrust as if EmDrive is a conventional propulsion system will lead to ambiguous results. Ideally, thrust should be calculated by measuring the acceleration of a freely suspended thruster, and then applying Newton’s laws.
This in itself is enough reason to ignore everything Shawyer says. Shawyer has demonstrated that he can't even do the most basic of force balances, and simply makes logically contradictory claims. Shawyer fails his own criteria so hard here, it can't even be used as a joke.
This list seems intended to do a run around to make sure that no one can ever do a competent experiment that demonstrates once and for all that the emDrive does not work. You can bet that if someone ever met all of those criteria, Shawyer would change the statement "thrust is proportional to Q, but Q < 50000 is a cutoff below which it doesn't work" to raise this cutoff to something physically impossible to build.
I am disappointed to see that Monomorphic "liked" this post, since it means we will never see his results. He already was on the verge of getting some good data with good calibration runs that brought the noise very low, before he stopped for months to completely change his setup.
Monomophic's experiment has already violated item 5,6,9. This means his experiment can not be used to invalidate EmDrive, even if he measure zero thrust with precision. So is Navy's new experiment. I can not stop thinking of preemptive defense. But it could only be me.
